Summary of Work: The objective is to test the hypothesis that there is/not a positive correlation between the presence of chemical contamination in specific aquatic environments and the incidence of abnormality among frogs from sites previously identified as normal vs abnormal. This study should be regarded as exploratory relative to the test of hypothesis and as a guide for further investigation utilizing controlled laboratory studies of any chemicals identified as possibly related to observed effects. The focus is on actual environmental mixtures rather than specific parent compounds; evidence from other sources continues to suggest that complex interactions among degradation products may contribute to enhanced detrimental biological activity. The experimental design consists of comparative water chemistry at timed intervals for previously identified sites where intensive study has the greatest probability of providing useful information. The water analysis is combine with scoring for incidence of abnormality among the resident anurans at various developmental stages. Quantitative spikes for all analytes in the field matrix under parallel conditions will be used to maintain accurate relative quantitation. We do not predict non recovery of useful data for any of the samples. In the final data we will account for any losses (based on the matrix spikes) or contamination (based on the field blanks) in the target list in a quantitative rather than speculative manner. Any degradation will be determinable as compound-dependent not sample-dependent. Broad spectrum analysis will also be conducted for a limited number of samples to look for unidentified analytes or degradation products in addition to the defined target list. Semipermeable membrane concentrators developed by the USGS will also be deployed to mimic biological membrane transport and concentrate unknown compounds such as PAH, retinoids and furans. These concentrates can be subjected to chemical analysis and in laboratory assays for biological activity. Additional assays will include frog embryogenesis, retinoid receptor binding, fish embryogenesis and endocrine response and a fish transgenic mutagensis assay.